Heat exchanger

ABSTRACT

A heat exchanger includes a plurality of flat tubes stacked with each other, and a tank connected at an end of each tubes to communicate with the tubes. The tank includes a tube joint part having a plurality of tube inserting holes, and a plurality of ribs extending in a tube width direction on the tube joint part. The ends of the ribs are positioned outside of the ends of the tube inserting holes. The tube joint part has a deformation allowable portion at an outside of the ends of the ribs so as to allow the tube joint part to be deformed in a tube longitudinal direction. The tube joint part has a plurality of approximately V-shaped cross-sections, in which the tube inserting hole and the rib are provided without a flat face therebetween.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-105815 filed on Apr. 1, 2005, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger. For example, the heat exchanger can be suitably used as a radiator of a water-cooled internal combustion engine in which heat is exchanged between cooling water and air.

2. Description of Related Art

U.S. Pat. No. 6,988,544 (corresponding to JP-A-2004-219044) discloses a heat exchanger including a core portion and a tank. In the core portion, a plurality of tubes and a plurality of corrugate fins are alternately stacked. The tank is disposed at the ends of the tubes in the longitudinal direction, and includes a core plate and a tank portion. The tubes are inserted into the core plate, and the tank portion is fixed to the core plate by caulking. The tank portion forms a space of the tank together with the core plate.

The core plate has tube inserting holes on a tube joint part, and a wall portion at a periphery of the tube joint part. The wall portion is bent approximately in perpendicular to the tube joint part. Moreover, ribs are formed parallel to the tube inserting holes on the tube joint part. A rigidity of the core plate is enhanced by connecting ends of the ribs to the wall portion such that a deformation of the core plate mainly due to an inner pressure can be reduced.

When the heat exchanger is used as a radiator for an automobile, the tubes may be damaged due to a generation of a thermal strain. Especially in a winter season, the tubes may be easily damaged because a temperature difference between cooling water and air is large. Moreover, the temperature difference may become large in a cross-flow heat exchanger, in which a longitudinal direction of the tubes corresponds to a shape of an aperture portion of a grill of the automobile, because one tube is easy to be cooled by air, while another tube is difficult to be cooled by the air.

When the tank is flexible in the tube stacking direction, that is, when the tank is independently deformable in the tube longitudinal direction in accordance with a thermal strain of each tube, the thermal strain can be absorbed in the tank. However, the thermal strain cannot practically be absorbed in the flexible tank.

As shown in FIG. 12, in a heat exchanger not having ribs on a core plate 20 of a tank, a thermal strain not absorbed by the deformation of the tank can be absorbed, because a tube joint part 22 of the core plate 20 can be deformed in the tube longitudinal direction X. The part 22 is deformed approximately in a circular arc. In FIG. 12, a dashed line represents a state in which the temperature difference between tubes 10 does not exist, and a full line represents a state in which the temperature difference of the tubes 10 is large. When the temperature difference is large, an affect of the thermal strain is concentrated on edge portions of the tube 10 in the tube width direction Z, because the tube joint part 22 is deformed approximately in the circular arc. Thereby, the stretching of the edge portion ES is larger than a stretching of a center portion CS in the tube width direction Z, as shown in FIG. 12. Thus, especially a large stress may be generated at the edge portion of the tube 10 in the tube width direction Z.

In contrast, in the heat exchanger disclosed in U.S. Pat. No. 6,988,544, the core plate is difficult to be deformed in the tube longitudinal direction, because the rigidity of the core plate is enhanced by the ribs. Thus, the margin for absorbing a thermal strain of the tube is small in the core plate such that a large stress is equally generated in all area in the tube width direction.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, it is an object of the present invention to provide a heat exchanger, in which a stress concentration on edge portions of a tube in the tube width direction is reduced and a stress is reduced in all area in the tube width direction.

According to a first example of the present invention, a heat exchanger includes a plurality of flat tubes stacked with each other in a tube stacking direction, and a tank connected at an end of each tubes in a tube longitudinal direction to communicate with the tubes. Each of the tubes extends in the tube longitudinal direction. The tank includes a tube joint part having a plurality of tube inserting holes, into which the ends of the tubes are inserted so as to be connected to the tank. The tank further includes a plurality of ribs on the tube joint part. The ribs extend in a tube width direction being perpendicular to the tube stacking direction and the tube longitudinal direction. The ends of the ribs in the tube width direction are positioned outside of the ends of the tube inserting holes. The tube joint part has a deformation allowable portion outside of the ends of the ribs in the tube width direction. The deformation allowable portion allows the tube joint part to be deformed in the tube longitudinal direction. The tube joint part has a plurality of approximately V-shaped cross-sections, in which the tube inserting hole and the rib are provided without a flat face therebetween.

According to a second example of the present invention, a heat exchanger includes a plurality of flat tubes stacked with each other in a tube stacking direction, and a tank connected at an end of each tubes in a tube longitudinal direction to communicate with the tubes. Each of the tubes extends in the tube longitudinal direction. The tank includes a tube joint part having a plurality of tube inserting holes, into which the ends of the tubes are inserted so as to be connected to the tank. The tank further includes a plurality of ribs on the tube joint part. The ribs extend in a tube width direction being perpendicular to the tube stacking direction and the tube longitudinal direction. The tank further includes a wall portion bent from a periphery portion of the tube joint part. The ends of the ribs in the tube width direction are positioned outside of the ends of the tube inserting holes, without being connected to the wall portion. The tube joint part has a plurality of approximately V-shaped cross-sections, in which the tube inserting hole and the rib are provided without a flat face therebetween.

According to the first or second example, a stress concentration on edge portions of a tube in a tube width direction can be reduced, and a stress can be reduced in all area of the tube in the tube width direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a front view of a heat exchanger according to a first embodiment of the present invention;

FIG. 2 is a perspective cross-sectional view of a tank and tubes in the heat exchanger shown in FIG. 1;

FIG. 3A is a front view of a single core plate shown in FIG. 2, and FIG. 3B is a bottom view of the single core plate shown in FIG. 3A;

FIG. 4 is a cross-sectional view of the single core plate taken along line IV-IV shown in FIG. 3B;

FIG. 5 is a cross-sectional view of the single core plate taken along line V-V shown in FIG. 3B;

FIG. 6 is a pattern diagram showing a deformation example of a core plate and a tube in the heat exchanger shown in FIG. 1;

FIG. 7 is a bottom view of a single core plate in a heat exchanger according to a second embodiment;

FIG. 8 is a cross-sectional view of the single core plate taken along line VIII-VIII shown in FIG. 7;

FIG. 9 is a bottom view of a single core plate in a heat exchanger according to a third embodiment;

FIG. 10 is a cross-sectional view of the single core plate taken along line X-X shown in FIG. 9;

FIG. 11 is a cross-sectional view showing a burring portion of a single core plate according to other embodiments; and

FIG. 12 is a pattern diagram showing a deformation example of a core plate and a tube in a conventional heat exchanger.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(First Embodiment)

A heat exchanger in a first embodiment is used for a radiator for cooling an engine (water-cooled internal combustion engine). As shown in FIG. 1, the heat exchanger includes an approximately cuboid-shaped core portion 1 formed by alternately stacking a plurality of tubes 10 and a plurality of corrugate fins 11 along up-and-down direction in FIG. 1. The stacking direction of the tubes 10 and the corrugate fins 11 is defined as a tube stacking direction Y. The corrugate fins 11 are made of aluminum alloy, and made in a corrugated shape so as to promote a heat exchange between air and cooling water. The tubes 10 have passages therein for flowing the cooling water of the water-cooled internal combustion engine (not shown) mounted to an automobile, and are formed by welding or blazing after a board made of aluminum alloy is bent in a predetermined shape.

In this embodiment, the longitudinal direction of the tubes 10 is defined as a tube longitudinal direction X, which corresponds to a horizontal direction in FIG. 1. The cross-sectional shape of the tubes 10 is formed in a flat shape such that a major diameter direction of the flat shape corresponds to an air flowing direction C, as shown in FIG. 2. A perpendicular direction to both the tube stacking direction Y and the tube longitudinal direction X is defined as a tube width direction Z. The tube width direction Z corresponds to the major diameter direction of the tubes 10 and the air flowing direction C.

As shown in FIG. 1, tanks 2, 3 are disposed at two ends of the tube 10 in the tube longitudinal direction X. The tanks 2, 3 have spaces 2 a therein, and extend approximately in the tube stacking direction Y. The ends of the tubes 10 in the tube longitudinal direction X are inserted into tube inserting holes 221 of the tanks 2, 3 such that the tanks 2, 3 are communicated with the tubes 10. The inserting holes 221 will be described in detail below. Thus, each passage of the tubes 10 and the space 2 a in the tanks 2, 3 are communicated with each other.

High-temperature cooling water discharged from the engine is distributed into the tubes 10 through the tank 2. The tank 2 includes an inlet pipe 20, which is connected to an outlet of the engine through a hose (not shown). In contrast, water cooled by exchanging heat with air flows out of each passage of the tubes 10, and the water is joined together in the tank 3. Then, the water is discharged toward the engine. The tank 3 includes an outlet pipe 30, which is connected to an inlet of the engine through a hose (not shown).

As shown in FIG. 1, side plates 4 for strengthening a structure of the core portion 1 are disposed in both the ends of the core portion 1 in the tube stacking direction Y. The side plates 4 are made of an aluminum alloy, and extend parallel to the tube longitudinal direction X such that the ends of the side plates 4 are connected to the tanks 2, 3. Each of the tanks 2, 3 include a core plate 20, a tank portion 21 and a packing (not shown). The tubes 10 and the side plates 4 are inserted into the core plate 20 so as to be fixed. A space 2 a of the tanks 2, 3 is constructed by the core plate 20 and the tank portion 21, as shown in FIG. 2.

The core plate 20 is made of aluminum alloy, and the tank portion 21 is made of resin, e.g., glass-reinforced nylon 66. The tank portion 21 is fixed to the core plate 20 by caulking. For example, the tank portion 21 is deformed such that protrusions 251 of the core plate 20 is fastened to the tank portion 21. The protrusions 251 will be described in detail below. When the tank portion 21 is fixed to the core plate 20, a packing made of rubber for keeping a sealed property is sandwiched between the core plate 20 and the tank portion 21.

As shown in FIG. 3B, the core plate 20 has a tube joint part 22, to which the tubes 10 are connected. A groove 20 a is formed in the all periphery of the tube joint part 22. The edges of the tank portion 21 and the packing are inserted into the groove 20 a having a cross-section approximately in a rectangular shape.

The groove 20 a has three portions. That is, the groove 20 a is formed of an inside wall portion 23, a bottom wall portion 24 and an outside wall portion 25. As shown FIGS. 4 and 5, the inside wall portion 23 is bent approximately perpendicular to the periphery portion of the tube joint part 22, and extends in the tube longitudinal direction X. The bottom wall portion 24 is bent approximately perpendicular to the inside wall portion 23, and extends in the tube stacking direction Y The outside wall portion 25 is bent approximately perpendicular to the bottom wall portion 24, and extends in the tube longitudinal direction X. The protrusions 251 are formed at the end of the outside wall portion 25.

The tube inserting holes 221 are formed in the tube joint part 22 of the core plate 20 at predetermined position in the tube stacking direction Y, and the tubes 10 are inserted into the holes 221 so as to be blazed. As shown in FIG. 3B, side plate inserting holes 222 are formed at both end portions of the tube joint part 22 in the tube stacking direction Y. The side plates 4 are inserted into the side plate inserting holes 222 so as to be blazed. The tube inserting holes 221 and the side plate inserting holes 222 are formed by a punching process, for example.

Moreover, ribs 223 are formed between the tube inserting holes 221 adjacent to each other, and between the tube inserting hole 221 and the side plate inserting hole 222. The ribs 223 are formed on the surface of the tube joint part 22 by pressing, for example, so as to be protruded and convex outside of the tank.

The peripheries of the inserting holes 221, 222 are protruded to be convex inside of the tank by the punching process. As shown in FIG. 4, between the inserting holes 221, 222 and the ribs 223, base faces 224 not protruded from the tube joint part 22 are left, because the pitch of the tubes 10 is relatively large in this embodiment. Boundary lines between the protruded portions of the inserting holes 221, 222 and the base faces 224 are defined as inserting hole boundary lines 225, when the tube joint part 22 is seen from the inside of the tank.

The inserting holes 221, 222 and the ribs 223 extend in the tube width direction Z, and the ribs 223 are longer than the inserting holes 221, 222 in the tube width direction Z. Further, the ends of the ribs 223 in the tube width direction Z are more peripheral than the ends of the inserting holes 221, 222 in the tube width direction Z. Specifically, the ends of the ribs 223 in the tube width direction Z are more outside than the ends of the inserting hole boundary line 225 in the tube width direction Z.

As shown in FIG. 3B, a dimension L1 in the tube width direction Z is provided between the end of the tube inserting hole 221 and the inside wall portion 23. Also, a dimension in the tube width direction Z between the end of the tube inserting hole 221 and the end of the rib 223 is defined as a rib protruding length L2. Then, the rib protruding length L2 may be about one third of the dimension L1.

The ends of the ribs 223 in the tube width direction Z do not extend to the inside wall portion 23. That is, the ends of the ribs 223 in the tube width direction Z are not connected to the inside wall portion 23. Therefore, the tube joint part 22 has a flat face 226 in a more peripheral area than the ends of the inserting holes 221, 222 and the ribs 223 in the tube width direction Z. The flat face 226 is flat over the all area in the tube stacking direction Y The deformation of the tube joint part 22 in the tube longitudinal direction X becomes easier due to the flat face 226. That is, the flat face 226 corresponds to a deformation allowable portion in this embodiment.

According to the first embodiment, the ends of the ribs 223 in the tube width direction Z are positioned more peripherally than the ends of the tube inserting holes 221 in the tube width direction Z such that the rigidity around the tube inserting hole 221 is enhanced. Therefore, even when the temperature difference between the tubes 10 is large, the tube joint part 22 adjacent to the tube inserting hole 221 is difficult to be deformed approximately in an arc such that the almost linear shape can be maintained in the tube joint part 22, as shown in FIG. 6. That is, the difference in the stretching of the tubes 10 between the edge portion and the center portion in the tube width direction Z becomes small such that the stretching of the tube 10 can be uniform in the all area in the tube width direction Z. Accordingly, the stress concentration on the edge portion in the tube width direction Z can be reduced in the tube 10.

Further, when the tank portion 21 is made of resin, the rigidity of the metallic core plate 20 greatly effects an entire rigidity of the tank. Therefore, the effect of the ribs 223 becomes relatively larger in the heat exchanger having the tank portion 21 made of resin.

Moreover, because the ends of the ribs 223 in the tube width direction Z do not extend to the inside wall portion 23, the flat face 226 is easy to be deformed in the tube longitudinal direction X. Therefore, when the temperature difference between the tubes 10 is large, as shown in FIG. 6, the core plate 20 is deformed in the tube longitudinal direction X by the deformation of the flat face 226. Accordingly, the thermal strain of the tubes 10 can be absorbed by the deformation such that the stress in the all area in the tube width direction Z can be decreased in the tube 10.

Accordingly, when the temperature difference between the tubes 10 is large, the stress concentration on the edge portion in the tube width direction Z and the stress in the all area in the tube width direction Z can be reduced in the tube 10.

Further, because the ribs 223 are formed between the tube inserting holes 221 adjacent to each other, the rigidity of the periphery of the tube inserting holes 221 can be enhanced such that the periphery of the tube inserting hole 221 is restricted to be deformed in an arc.

Furthermore, the ends of the ribs 223 in the tube width direction Z are more peripheral than the ends of the inserting hole boundary line 225 in the tube width direction Z. Thereby, when the temperature difference between the tubes 10 is large, the deformation is generated at a more peripheral part than the inserting hole boundary line 225 such that the stress concentration on the inserting hole boundary line 225, i.e., bent portion, can be reduced.

Moreover, because the rib protruding length L2 is about one third of the dimension L1, the rigidity around the tube inserting holes 221 is enhanced. Therefore, the periphery of the tube inserting hole 221 is restricted to be deformed in an arc, and the flat face 226 is easily deformed in the tube longitudinal direction X.

(Second Embodiment)

The above-described embodiment is only an example for the heat exchanger of the present invention. It is to be noted that various changes and modifications will be become apparent to those skilled in the art.

As shown in FIGS. 7 and 8, the tube inserting holes 221 may be formed by a burring process. In the second embodiment, the other parts can be made similarly to the above-described first embodiment.

(Third Embodiment)

As shown in FIGS. 9 and 10, when the pitch between the tubes 10 adjacent to each other is small, the tube inserting hole 221 and the rib 223 may be connected without the base face 224. In this case, the tube inserting holes 221 are formed at tip ends of plural V-shaped grooves in cross-section, and the ribs 223 are formed at opposite tip ends of the plural V-shaped grooves in cross-section.

The core plate 20 has a plurality of approximately V-shaped cross-sections such that the strength of the core plate 20 is increased. The V-shaped parts can be blazed together to form the tube inserting holes 221 and the ribs 223, after being separately formed. In this case, the both ends of the V-shaped grooves in the tube width direction Z are connected to the flat face 226 smoothly in a curve. In the third embodiment, because the tube joint part 22 of the core plate 20 is formed in zigzag without a flat surface between the rib 223 and the tube inserting hole 221 in the tube stacking direction, the performance of the heat exchanger can be more improved.

(Other Embodiments)

As shown in FIG. 11, burring portions 227 may be formed at the peripheries of the tube inserting holes 221 in the above-described embodiments.

In the above-described embodiments, the rib 223 is formed at each portion between adjacent tube inserting holes 221 in the tube stacking direction Y. However, the ribs 223 may be formed partially between the adjacent tube inserting holes 221 in the tube stacking direction Y. For example, the ribs 223 may be formed in every other portion between the holes 221.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

1. A heat exchanger comprising: a plurality of flat tubes stacked with each other in a tube stacking direction, each of the tubes extends in a tube longitudinal direction; a tank connected at an end of each tubes in the tube longitudinal direction to communicate with the tubes, wherein the tank includes a tube joint part having a plurality of tube inserting holes, into which the ends of the tubes are inserted so as to be connected to the tank; and a plurality of ribs on the tube joint part, wherein the ribs extend in a tube width direction being perpendicular to the tube stacking direction and the tube longitudinal direction, wherein: ends of the ribs in the tube width direction are positioned outside of ends of the tube inserting holes; the tube joint part has a deformation allowable portion outside of the ends of the ribs; the deformation allowable portion allows the tube joint part to be deformed in the tube longitudinal direction; and the tube joint part has a plurality of approximately V-shaped cross-sections, in which the tube inserting hole and the rib are provided without a flat face therebetween.
 2. A heat exchanger comprising: a plurality of flat tubes stacked with each other in a tube stacking direction, each of the tubes extends in a tube longitudinal direction; a tank connected at an end of each tubes in the tube longitudinal direction to communicate with the tubes, wherein the tank includes a tube joint part having a plurality of tube inserting holes, into which the ends of the tubes are inserted so as to be connected to the tank; and a plurality of ribs on the tube joint part, wherein the ribs extend in a tube width direction being perpendicular to the tube stacking direction and the tube longitudinal direction, wherein: the tank further includes a wall portion bent from a periphery portion of the tube joint part; ends of the ribs in the tube width direction are positioned outside of ends of the tube inserting holes, without being connected to the wall portion; and the tube joint part has a plurality of approximately V-shaped cross-sections, in which the tube inserting hole and the rib are provided without a flat face therebetween.
 3. The heat exchanger according to claim 1, wherein: the ribs are disposed between the tube inserting holes adjacent to each other in the tube stacking direction.
 4. The heat exchanger according to claim 1, wherein: the tank includes a core plate made of metal, and a tank portion made of resin for forming a tank space together with the core plate; and the core plate includes the tube joint part joined to the tube, and a tank joint part joined to the tank portion.
 5. The heat exchanger according to claim 1, wherein: the tubes are fixed to the tube inserting holes by blazing.
 6. The heat exchanger according to claim 1, wherein: the tube inserting hole is provided to have a burring portion in its periphery.
 7. The heat exchanger according to claim 1, wherein: the ribs are convex protruding outside from the tank at tip ends of the V-shaped cross-sections; and the deformation allowable portion is connected to the ends of the ribs in a curve.
 8. The heat exchanger according to claim 2, wherein: the ribs are disposed between the tube inserting holes adjacent to each other in the tube stacking direction.
 9. The heat exchanger according to claim 2, wherein: the tank includes a core plate made of metal, and a tank portion made of resin for forming a tank space together with the core plate; and the core plate includes the tube joint part joined to the tube, and a tank joint part joined to the tank portion.
 10. The heat exchanger according to claim 2, wherein: the tubes are fixed to the tube inserting holes by blazing.
 11. The heat exchanger according to claim 2, wherein: the tube inserting hole is provided to have a burring portion in its periphery.
 12. The heat exchanger according to claim 2, wherein: the ribs are convex protruding outside from the tank at tip ends of the V-shaped cross-sections; the tube joint part has a deformation allowable portion outside of the ends of the ribs; and the deformation allowable portion is connected to the ends of the ribs in a curve. 